At the macroeconomic level the principal aim of this project is to develop an interactive economic-demographic model of U.S. experience over the past five decades that centers on the causes and effects of the long swing in fertility and its relation to "relative income." We plan too to develop a more comprehensive picture of the effects of the sing by analyzing several social as well as economic variables, and to do at least some preliminary work on a few other developed countries with similar experience. At the microeconomic level the proposed research includes the nature and trend during economic development of the prevalence of deliberate fertility control, the relation of this to trends in fertility differentials by socioeconomic status, and the factors lying behind the SES-fertility differentials both for those who do and those who do not regulate their fertility. This involves chiefly theoretical work on natural fertility, the relevance of the "bequest motive" to agricultural populations, and the mechanisms of interdependent preferences underlying the relative income variable. Work in the current year was focused on primarily analyzing the macroeconomic effects of the long swing in fertility and consequent shifts in the relative numbers and incomes of younger versus older workers.